There are 4 vedas - Rigveda, Yajurveda, Samaveda and Atharvaveda.
But in several places few scriptures are mentioned as 5th Veda, such as:
The boon-giving great one then taught Sumanta, Jaimini, Paila, his son Suka, and Vaisampayana, the Vedas having the Mahabharata for their fifth. -Adi Parva: Adivansavatarana Parva of Mahabharata
vedāś catvāra uddhṛtāḥ
pañcamo veda ucyate
The four divisions of the original sources of knowledge [the Vedas] were made separately. But the historical facts and authentic stories mentioned in the Purāṇas are called the fifth Veda. -SB 1.4.20
Similarly, I heard that Epics (Ramayana and Mahabharata) are called as 5th Veda or sometimes Epics and Puranas collectively called as 5th Veda.
So, is there any scripture where Ramayana is mentioned as 5th Veda or Epics collectively are mentioned as 5th Veda?